The work proposed in this project is designed to study in detail the interactions of concanavalin A in cell surface. Special attention is directed towards elucidating factors in serum which alter these interactions. Also, a study of elements of tumor cell membranes affecting the cells behavior towards membrane probes is detailed. Of particular import is the isolation and characterization of a protein found in canine serum which greatly enhances the agglutinability of otherwise poorly agglutinable cells. The mode of action of the purified protein will be studied in detail also.